Field
Embodiments described generally relate to methods for treating oil-based drilling fluids. More particularly, the embodiments described relate to methods for treating oil-based drilling fluids with fluid loss additives that include one or more hydrocarbon resins.
Description of the Related Art
Subterranean deposits of natural resources such as gas, water, and crude oil are commonly recovered by drilling wellbores to tap subterranean formations or zones containing such deposits. Various fluids are employed in drilling the wellbore and preparing the wellbore for the recovery of the natural resources. For example, a drilling fluid can be circulated through a wellbore that can serve a number of purposes including: lubricating the drilling tool and drill pipe, suspending and transporting formation cuttings to the surface for filtering and disposal, holding the cuttings in suspension in the event of a shutdown of the drilling operation, and counterbalancing subterranean formation pressures to prevent the inflow of gas, oil, or water from permeable rock formations. Drilling fluids, also referred to as “drilling muds,” can be water-based or organic-based, such as oil-based and so-called synthetic-based drilling fluids. The organic-based drilling fluids are frequently employed as invert emulsions with high concentrations of the organic-based fluid mixed with water in the presence of emulsifiers.
For a drilling fluid to perform its functions the drilling fluid must stay in the wellbore. Often, undesirable subterranean formation conditions are encountered during drilling during which substantial amounts of the drilling fluid can be lost to the formation. The hydrostatic pressure of the drilling fluid must be greater than the pressure of the fluids in the formation to prevent formation fluids from entering the wellbore. As a result, there is a tendency for the drilling fluid to invade the permeable subterranean formations. Drilling fluid can leave the wellbore through large or small fissures or fractures in the formation, which can be pre-existing or drilling-induced. Generally, the solids of the drilling fluid are filtered out onto the walls of the wellbore forming a filter cake, which functions as a barrier. The drilling fluids should be formulated so as to keep the deposited filter cake permeability as low as possible in order to maintain a stable borehole and minimize filtrate invasion of, and damage to, potentially productive strata in the subterranean formation. Fluid-loss additives can be added to the drilling fluid to reduce the loss of the drilling fluid to the surrounding formation. However, unacceptable losses of drilling fluid to the surrounding subterranean formation can still occur despite the type of drilling fluid employed and the fluid loss additive used.
There is a need, therefore, for improved fluid loss additives that can reduce the loss of drilling fluids to the formation while drilling.